Northstar Engines and System Technical Discussion Discussion, Changing Coolant and the Right Number of Tablets in Cadillac Engine Discussion; Originally Posted by Ranger
They are a cooling system supplement (sealant). The purpose is to prevent nuisance leak &amp; seepage. ...

Re: Changing Coolant and the Right Number of Tablets

Originally Posted by Ranger

They are a cooling system supplement (sealant). The purpose is to prevent nuisance leak & seepage. They can be purchased at any GM dealer or Walmart, or most parts stores. If you get them from other than a dealer look for Barsleaks products. The tabs product code is HDC and the powdered version is G12BP. Put them in the radiator hose, NOT the surge tank. Do a search for Barsleaks, tabs, cooling system supplement, HDC, G12BP. You should find enough reading to keep you out of trouble for days.

Ranger, when I was at my local parts desk at the Caddy dealer last week picking up a water pump, I asked them about installing the pellets. They told me that they no longer put them in N* engines b/c they tend to clog up the radiator? They also no longer carry them in stock for sale. Any truth to this notion? mr_mr11

Re: Changing Coolant and the Right Number of Tablets

If that were true, all the earlier Northstars plus the 4.9's, 4.5's & 4.1's would have clogged radiators and we would certainly have heard complaints here. I think the reason that they quit using them is because they make the coolant look muddy, thus people where complaining that the cooling system is going bad and asking that the coolant be changed while under warranty. Especially if they have been on the internet and were reading Dex-Cool horror stories.

Re: Changing Coolant and the Right Number of Tablets

I replaced my North*, and refreshed everything. Just a little suggestion about installing your waterpump. ( You can do it yourself ).... When using that special socket installing the waterpump, & as you turn it to lock it in place, notice the bent-up tabs...... They will flatten very easy, if you use a breaker bar!! Careful not to go to tight, to the poing you flatten the tabs, and 'spin' the waterpump past the stops. I was told to use just grease at the '0' ring area, and it's to keep the pump from corroding / rusting.

Re: Changing Coolant and the Right Number of Tablets

Originally Posted by Mountie

I replaced my North*, and refreshed everything. Just a little suggestion about installing your waterpump. ( You can do it yourself ).... When using that special socket installing the waterpump, & as you turn it to lock it in place, notice the bent-up tabs...... They will flatten very easy, if you use a breaker bar!! Careful not to go to tight, to the poing you flatten the tabs, and 'spin' the waterpump past the stops. I was told to use just grease at the '0' ring area, and it's to keep the pump from corroding / rusting.

Mountie - I echo your comments on the water pump replacement however I had to use an impact wrench to get my old one off and get the new one back on - the handy socket I purchased from Napa worked well.

Re: Changing Coolant and the Right Number of Tablets

Originally Posted by 26TP

....And finally is the 50/50 mix rule super critical?

It's important enough to put some effort into measuring carefully if you are doing the mixing.

Not only does the Dex-Cool provide freeze protection. It also elevates the boiling point of the mixture. And you really want the boiling point of the mix to be in the neighborhood of 265 degrees F @ 15 PSI pressure. If you end up with less than 50% Dex-Cool and more than 50% water, the pressurized mixture will vaporize at less than 265 degrees F @ 15 PSI. How much less won't matter when you are stranded on the side of the highway some dark and stormy night.

Re: Changing Coolant and the Right Number of Tablets

I picked up some cooling system seal tabs from the dealer today, part #3634621. I plan on putting all 6 tabs in the system along with fresh 50/50 Dexcool mix. I understand not to flush the cooling system with fresh water, just drain and refill, correct? One other question, the parts guy and the package instructions say to crush up the tablets, add to the coolant and pour directly into the radiator, so is that the best way, mix and pour into the surge tank?

Re: Changing Coolant and the Right Number of Tablets

Originally Posted by racinrod67

I picked up some cooling system seal tabs from the dealer today, part #3634621. I plan on putting all 6 tabs in the system along with fresh 50/50 Dexcool mix. I understand not to flush the cooling system with fresh water, just drain and refill, correct? One other question, the parts guy and the package instructions say to crush up the tablets, add to the coolant and pour directly into the radiator, so is that the best way, mix and pour into the surge tank?

Re: Changing Coolant and the Right Number of Tablets

racinrod, If your manual calls for the cooling system tablet supplement, it generally specifies 3 tablets crushed in the lower (return) radiator hose. Using the whole package is unnecessary overkill and could very well lead to clogging of some cooling passages.

As AJ's lengthy thread (referenced above) says, the supplement tablets were and are not designed to be a cure or preventative for head gasket gas leaks into the coolant; rather they were used to seal nuisance weeps from gasket irregularities and aluminum casting pososity. General Motors is not the only engine manufacturer to use the product, not by a long shot.

Drain as much old coolant as possible and refill with a 50/50 mix of the coolant specified in your manual.

Re: Changing Coolant and the Right Number of Tablets

They need to be crushed when putting them in a radiator because of the oil or trans cooler line in the side tank. That prevents you from putting whole tabs in there. On the Northstar you can just pop the whole tab in the radiator hose.